Meaning victory is certain, this expression seems to have appeared in print for the first time in 1842, when a Welsh sportswriter used it. Though the phrase may have originated in sports, it could have its roots in local elections settled by voice vote in rural England. These elections, associated with great noise, came to be called “shoutings.” There is no proof of this, but perhaps some candidate or observer of the day was so sure of the outcome of a “shouting” that he remarked it's all over but the shouting and the phrase passed into popular usage.